U.S. Pat. No. 6,985,512, Asynchronous Spread-Spectrum Communications, by Scott A. McDermott, and Leif Eric Aamot, which is incorporated herein by reference in its entirety, describes a method wherein a receiver of spread spectrum can receive communications from multiple devices that use the same spreading code. Because the code-phase of the signals arriving from the various transmitters is not synchronized, and because the spreading code is orthogonal to itself at different phases, the receiver can discriminate and decode various overlapping messages. The system assumes that the code-phase of the various transmitters is asynchronous. In the case where the code phases of two (or more) different transmitters happen to be substantially identical, reception may fail which can cause the higher communication layers to invoke re-transmission.
A similar idea was described in an earlier NASA paper entitled “A Code Phase Division Multiple Access (CPDMA) Technique for VSAT Satellite,” by Bruno, R., McOmber, R., and Weinberg, A, which is also incorporated herein by reference in its entirety. Bruno describes a reference concept and architecture for implementing a CPDMA bulk demodulator/converter. More importantly, the paper provides an upper bound for the number of independent transmitters that can be reliably decoded using CPDMA.